This invention relates to telephone systems and more particularly to a dial plan mapper used for routing telephone calls to different telephone networks.
In order to provide adequate utility, a Voice over IP (VoIP)-based Internet Telephony system must provide connectivity to the hundreds of millions of telephones on today""s Public Switched Telephone Network (PSTN). Circuit-switched telephony is based on the E.164 international addressing standard. Internet applications are based on the Internet Protocol (IP) address space and the Domain Name System (DNS). In order to provide telephony services over IP networks (VoIP), there must be a translation between E.164 addresses and Internet hosts.
There are many challenges to interconnecting these large systems, not the least of which is the different addressing schemes and signaling protocols used by the two systems. The E.164 addressing scheme used with PSTN comprises a string of 1-15 decimal digits with allocation by country and geographic area. VoIP on the other hand uses 32 bit IP addresses that are assigned to Internet hosts. The PSTN signaling protocol uses a Foreign Exchange Office (FXO), Foreign Exchange Station (FXS), or Ear and Mouth (EandM) for analog signaling and Q.931, Q.Sig or Common Channel Signaling System #7 (SS7) for digital signaling. VoIP uses H.323, Session Initiation Protocol and Session Description Protocol (SIP+SDP), Simple Gateway Control Protocol (SGCP), Media Gateway Control Protocol (MGCP) and many other types of signaling protocols.
Quality of Service (QoS) for PSTN and VoIP are also different. QoS for PSTN is based on one universal level with 300-3400 Hz voice channels, sampled at 8 kHz, and transmitted digitally as 64 kbps Pulse Code Modulation (PCM). QoS for VoIP varies from xe2x80x9cbest effortxe2x80x9d to xe2x80x9cguaranteed delayxe2x80x9d and uses protocols such as Resource Reservation Protocol (RSVP) and packet scheduling algorithms such as Weighted Fair Queuing (WFQ).
Prior efforts to marry these two address spaces have attempted to embed one address space in the other. For example, host names are provided in the form 2048.264.508.1.pstn.net. Alternatively, every endpoint is required to have two addresses. None of these efforts have proven effective. Furthermore, these mapping schemes do not operate efficiently with locally administered short-cut dial plans, such as those used with a Private Branch Exchange (PBX).
Thus, a need remains for a single translation solution for efficiently mapping between different VOIP and circuit-switched telephone systems.
Circuit-switched telephony is based on the E.164 international addressing standard. Internet applications are based on the IP address space and the Domain Name System (DNS). In order to provide telephony services over IP networks (known as Voice over IP, or VoIP), a dial plan mapper manages the translation between E.164 addresses and Internet hosts. The dial plan mapper at the same time translates between the variety of addressing (e.g. private dialplan), session protocol, and quality of service mechanisms present in today""s IP and circuit-switched network environments.
A dial string is received from a session application that interfaces with a packet switched or circuit-switched system such as VoIP, PSTN, PBX, etc. Regular expression match patterns are compared with the dial string. The dial plan mapper identifies one of the match patterns providing a longest match with the dial string and outputs call configuration information associated with the identified match pattern. The configuration information contains call parameters necessary for completing the telephone call whatever session protocol is associated with the call destination. The configuration information indicates what destination system the session application needs to talk to for establishing the call, what protocol to use for talking with the destination system and how to manipulate the input dial string to construct an output dial string usable by the destination system.
The dial plan mapper allows normal circuit-switched telephones to be used with VoIP and allows existing dialing conventions to be used unchanged. As far as the dial plan mapper is concerned, there is no difference between a call originated locally on a phone connected to a host containing the dial plan mapper and a call originated through a PBX or PSTN switch connected to the host via either analog or digital trunks. When calls arrive over the IP network, the dial plan mapper maps from the destination telephone number provided in the session protocol (usually an E.164 number) to the proper local interface (local FXS line or outbound trunk) for completing the call over the legacy voice network.
The mapping scheme accommodates the styles of phone numbers in use internationally, through the PSTN and through internal private voice networks. For example, full E.164 international numbers like +1 44 736 5534, national numbers like 1 900 746-6379, local numbers like 435 8251, internal company dialing schemes like 6-2231, with outside-line escapes such as 8- and 9-. These different numbering schemes are dealt with in the same way, rather than through a set of ad hoc rules as generally applied in other systems.